INTRODUCTORY ESSAY. 185 ing its valley from an elevation of 1000 feet, as far as its sources in the Walanchun and Kanglachem passes (16-17,000 feet). This journey was made during winter, and therefore gave less important results botanically than would have been obtained at a more favourable season. It "is unnecessary to dwell at length on the general charac- ter of the surface of Nipal, as to do so would only be to reca- pitulate what has already been said regarding the Himalaya in general. Little is known of the details of the higher parts of jfche chain, or of the position of the axis of the Hi- malaya, which probably lies in general very far back. The political frontier of Tibet is usually far to the south of the axis, the upper part of the course of most- of the rivers of the Indian slope of the chain belonging almost invariably to Tibet. Two giant masses project from the axis towards the Indian plain, the culminant peaks of which form a conspicuous feature from Kathmandu, and even from the Gangetic plain, so that their elevation has been approximately determined; that of Dhawalagiri being 27,600 feet, and that of Gosainthan 24,700 feet. By these masses the whole of Nipal is divided into three great river-basins,—that of the Karnali or Gogra to the westward, that of the Gandak in the centre, and that of the Kosi or Aran to the eastward*. These divisions are no doubt highly natural. For our purposes a subdivision is little necessary, from our very slight acquaintance with the flora of any part of Nipal except that in which Dr. Wallich collected, and it will suffice to distinguish eastern, central, and western Nipal, whenever it appears requisite to assign particular lo- calities to our plants. * gfee an excellent paper by Mr. Hodgson in the Journal of the Asiatic Society of Bengal, in which the importance of the riv-er-basins as geographical divisions is forcibly pointed out. Mr. Hodgson has however misunderstood Captain Herbert's views, which are certainly the same as his own in that re- spect. Captain Herbert's proposition, that the line of the great peaks inter- sects the riverrbasiua (and is therefore not the true axis of the Himalaya), was the first enunciation of a v6ry important fact in physical geography, the true significance of whieh is not j>ot (My appreciated.